1. Field of the Invention
The present invention relates to an abnormality detection apparatus for predicting occurrence of abnormality in a vehicle alternator and outputting an alarm signal when necessary.
2. Description of Related Art
There is known an abnormality detection apparatus configured to detect an abnormality of a vehicle alternator on the basis of an output voltage of the vehicle alternator. For example, refer to Japanese Patent Application Laid-open No. 2005-102436. This abnormality detection apparatus filters an output voltage of the vehicle alternator by a filter having a predetermined pass band, and determines that there is abnormality in the vehicle alternator if the difference between a maximum and a minimum of the filtered output voltage exceeds a predetermined value.
However, although the above abnormality detection apparatus can detect occurrence of an abnormality in the vehicle alternator, it cannot predict occurrence of an abnormality in the vehicle alternator, and issue an alarm signal if necessary.
In recent years, a growing number of vehicles are provided with an engine auto start/stop function enabling, for example, to stop and restart a vehicle engine automatically at an intersection. In such vehicles, a rectifier device (particularly, soldered portions of rectifying elements) of a vehicle alternator tends to malfunction due to thermal fatigue with higher frequency compared to vehicles not provided with the auto start/stop function, because electrical loads are turned on and off more frequently when the auto start/stop function is provided than when it is not provided. If it is possible to issue an alarm before an abnormality due to accumulation of thermal fatigue occurs, parts which are going to malfunction can be replaced before they stop functioning.